Add source icon for collection based on collection members
The source workflow (PDF/WORD/XML) of a collection is dependent on the books in the collection, so:
- When collection is created, the "source" is null (show no icon in "source" column in the dashboard)
- When a book is added, match collection source to book source
- If books in collection have more than one source, show no icon (this can be improved later with a icon to show multiple sources)